This invention relates in general to communication systems, and more particularly to a group emergency call system for alerting a group of people connected to a central office exchange in the event of an emergency.
Group emergency call systems are intended for use by volunteer fire personel, civil defence, or other groups requiring quick and simultaneous distribution of a message from a single individual to a number of other individuals. This service has historically been used in rural areas to provide one-way communication from a control position to a preselected group or groups of individuals. The traditional method of providing this service has been to instal an adjunct switching system in the central office exchange that is cross-connected to lines dedicated for emergency use by the group emergency call system. Examples of such prior art cross-connectedadjunct or add-on systems are the 291 Emergency Reporting System by Tellabs Inc., and the Emergency Out Dial System manufactured by Message Processing System, Inc.
Such prior art systems suffer from the disadvantages of being expensive and complex, and requiring external maintenance terminals and sophisticated electronic equipment. Furthermore, such add-on emergency group call systems are incapable of providing standard central office or PBX call functions such as automatic call forwarding from an emergency hunt group subscriber set to a further set in the exchange. For example, the afformentioned 291 Emergency Reporting System utilizes a siren for notifying subscribers whose sets have been placed in call forward or do-not-disturb modes.